Adjustable trigger mechanism



April 1, 1952 F. D. H-OPPERT 0,

ADJUSTABLE TRIGGER MECHANISM Filed July 27, 1948 Fi l 15E? D HEI F F EI L fi UWZ L/KW hum- Patented Apr. 1, 1952 UNETE STATES PATENT DFFICE Application July 27, 1948, Serial No. 40,972

(Granted under the act of March 3, 1883, as

2 Claims.

amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to an adjustable trigger mechanism and more particularly to a mechanism for eliminating the creep in trigger pulls of firearms.

It is most disconcerting to a shooter of firearms, particularly in target shooting, to have an abnormal amount of creep in the trigger pull just prior to release of the sear. In certain types of firearms it is especially diflicult to eliminate creep from the trigger pull. One of such firearms is the U. S. rifle, cal. .30 M1 known as the Garand rifle. Due to the accumulation of manu facturing tolerances the trigger pull of such firearm is not always crisp and free from creep.

Accordingly it is an object of this invention to provide a device for substantially eliminating the creep from trigger mechanisms.

A particular object of this invention is to provide an adjustable trigger mechanism for the U. S. rifle, cal. .30 M1 and for substantially eliminating the creep from the trigger mechanism of such firearm.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a side elevational View of the trigger guard housing of the M1 rifle embodying this invention.

Fig. 2 is an enlarged detail view of the sear and trigger shown just prior to release of the hammer.

Fig. 3 is a view similar to Fig. 2 but showing the position of the related parts when the primary sear is in engagement with the hammer.

In Fig. 1 there is shown in assembled relation a trigger guard housing III of the U. S. rifle, cal. .30 M1. A hammer II is pivotally mounted on such housing in the well known manner, as disclosed in the Garand Patent 2,377,338 of June 5, 1945 and a hammer spring I2 in spring housing I3 is provided to bias hammer II forwardly to discharge a cartridge. The rear end of spring housing I3 is pivotally secured to housing ID by a pin 23. The rearwardly extending end of hammer II is bifurcated so that such end of the hammer can readily pass over a trigger IS in the usual fashion. Each portion of the bifurcated end is provided with a front shoulder or lug I and a rear shoulder or lug It. Trigger I6 is also pivotally mounted on housing III by the same pin 23 utilized for mounting spring housing I3. Such trigger is provided on the upper end thereof with a hammer engaging transverse sear lug I'I protruding from each side thereof. Lug I1 is engageable with lugs I5 provided on hammer II as will be later described.

A primary sear I8 is pivotally mounted on trigger I6 also in a well known manner. In theaMl rifle trigger mechanism, primary sear I8 is provided with a pair of forwardly projecting lugs (not shown) which contact the rear end of the spring housing I3. The hammer spring I2 is therefore also utilized for the trigger spring in order that sufiicient bias may be exerted against the trigger to provide a trigger pull of desired weight and also to insure that lugs I5 of hammer II.will engage sear lug I! of trigger I6. In the operation of the U. S. rifle, cal. .30 M1 the reciprocating bolt of such firearm (not shown) recoils and strikes hammer II thus pivoting it rearwardly in a counterclockwise direction as shown in Fig. 1. Trigger It being held rearwardly at the moment of discharge of the firearm has rocked lug I'I forwardly out of engagement with lugs I5 of hammer H thus bringing primary sear I8 upwardly so that primary sear I8 can engage lugs I4 of hammer II thus holding the hammer in the cooked position. Upon release of trigger I6, primary sear I8 slides off of lugs I4 whereupon sear lug II of trigger I6 engages lugs I5 of hammer II thus holding the hammer in the cooked position when the trigger is in its normal or forward position. This operation is all conventional.

It is apparent to those skilled in the art that in the conventional trigger mechanism above described that hammer spring housing I3 exerts considerable bias against the trigger I6 which therefore makes the weight of the trigger pull rather indefinite by reason of the fact that the bias exerted by hammer spring I2 is considerable. Accordingly a heavy trigger pull and one which has considerable creep is commonly found, therefore in the practice of this invention, the forwardly projecting lugs (not shown) of sear I8 are removed, preferably by grinding, thus removing the bias of hammer spring I2 from primary sear I8.

A spring 20 is mounted in back of primary sear I8 and may be fastened to trigger I6 by a block 2I brazed or otherwise secured to such trigger. Spring 20 is arcuately shaped as shown and bears against the upper part of sear I8. A screw 22 provided in block 2I contacts spring 20 whereby the tension of such spring against; sear l8 may be readily varied, thus also may the weight of the trigger pull be readily adjusted to suit.

In the operation of this improved trigger mechanism, spring 20 is normally forced back against screw 22 immediately prior to release of sear lug H from hammer lugs 15. Spring 20 is adjustable to provide sufficient force against sear 18 to insure that such sear will always engage hammer lugs 14 in semi-automatic fire as the bolt of the firearm rotates hammer II in a counterclockwise direction as shown in Fig. 3, on the recoil stroke of such bolt. Thus the firearm is always maintained in a safe condition so that the hammer will not follow the bolt forwardly to prematurely discharge a cartridge. Many prior art improvements to the Ml'rifle trigger mechanism have modified such mechanism to such an extent as to destroy this desirable function of primary sear l8 thus making the firearm relatively unsafe.

As. force of spring 2:1 is of considerably lesser magnitude than that of hammer spring 42 against primary sear IS, a longer preliminary pull isv permissible. before any substantial resistancev is met by the primary sear is striking the back of hammer H and: springlll striking the end. of screw 22. Thus when the preliminary pullis taken up only a very small engagement of sear lug H with lugs 15 remains thereby providing a much lighter trigger pull which is sub.- stantially free from creep.

From the. foregoing description it is clearly apparent to those skilled in the art that therei s here provided a simple and effective device for reducing the weight of the trigger pull as well as substantially eliminating the creep from the trigger pull and yet at the same time maintaining the desirable functional and safety features of the prior art trigger mechanism.

Icla-im:

1. A trigger mechanism for a firearm having a pivoted hammer movable through a limited arc to a cocked position and a spring biased plunger for operating the hammer, said mechanism comprising a trigger, means on said trigger engageable with the cooked hammer in one position of said trigger, second means on said trigger engageable with the cocked hammer in another position of said trigger, a leaf spring mounted on said trigger directly biasing said first mentioned means against said trigger, and adjusting means engageable with said spring whereby the weight of the trigger pull may be varied.

2. A hammer and trigger mechanism comprising a pivoted hammer movable through a limited arc from a cocked position to a fired position including an arm having forwardly and rearwardly extending shoulders, a spring biased plunger for operating said hammer, a pivoted trigger having a lug thereon engageable with said forwardly extending shoulders of said hammer in the cooked position thereof when said trigger is in a neutral position, a sear pivotally mounted on said trigger and engageable with said rearwardly extending shoulders of said hammer in the cooked position thereof when said trigger is in a pulled position, a leaf spring secured to said trigger and arranged to directly bias said sear forwardly against said trigger, and screw means engageable with said spring whereby the bias of said spring is adjusted toprovide a desired trigger pull.

FILSER D. HOPPERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

